PICOSUN™ Atomic Layer Deposition Systems FAQ
Q: What are the advantages of PICOSUN™ ALD process tools?
A: The main advantage of our products is the ability to produce extremely uniform high quality thin films with short cycle times and good repeatability. Other advantages include ease of use, quick maintenance and highly reliable operation. We also offer broad range of reaction chambers, precursor sources and substrate loaders to choose from. PICOSUN™ ALD process tools are designed and assembled with years of experience in ALD equipment. All in all, we are talking about supreme quality at reasonable price.
Q: What are PICOSUN™ ALD tools designed for?
A: PICOSUN™ ALD process tools are designed for processing of top quality thin films by thermal ALD. This is what they are good at. And they do it extremely well.
Q: What should I take into account when selecting an ALD process tool?
A: ALD is a thin film deposition method, which is capable of processing extremely conformal, highly uniform and dense thin films with really low amount of defects. If this is what you are looking for, you should seriously consider buying an ALD process tool. A good quality ALD tool can deposit uniform films with short cycle times even on large area substrates. We take the quality of our product range truly seriously and are eager to prove it to our customers by film demonstrations. This is because we feel that high quality research or production can only be done with finest quality process equipment. Our CTO Sven Lindfors has designed ALD process tools with the inventor of ALD and member of Picosun Board of Directors Dr. Tuomo Suntola since 1974. This means that we have the longest possible ALD experience in our company. Many of the sophisticated ALD innovations found in Picosun products have been developed over long period of time. Some companies, who are selling ALD process equipment, have only a couple of years of ALD experience. As an analogy, would you buy an aeroplane from a company that has two years of experience in aviation technology?
Q: What is the relation between cycle time and film non-uniformity in ALD processes?
A: An ALD growth cycle consists of precursor pulses followed by inert gas purges. A two component ALD process proceeds as follows: precursor A pulse -> purge -> precursor B pulse -> purge. This growth cycle is repeated as long as desired film thickness is reached. In case the purge steps are too short, the precursor pulses overlap and film uniformity will typically degrade. However, in a well designed ALD process tool, uniform high quality films can be achieved even with short cycle times. A good example of PICOSUN™ ALD process tool quality is that our customers have obtained < 1 % ( standard deviation / average) aluminum oxide film non-uniformity on 6’’ wafer with 2.2 seconds cycle time. Growth of 100 nm aluminum oxide film requires about 1000 growth cycles. Therefore a highly uniform 100 nm aluminum oxide film can be deposited in 37 minutes in our ALD process tools. Some ALD systems on the market require longer than 30 seconds cycle times, which means that it takes over 8 h 20 min to grow a 100 nm aluminum oxide film. Good film non-uniformities and short process times are a must in production, but they also enable productive high quality research work.
Q: What kind of customer support will I get, if I buy a PICOSUN™ ALD process tool?
A: First of all, every PICOSUN™ process tool is inspected and process tested prior to shipment to a customer. The testing continues at the customer site with process runs and user training. The process tool also includes a comprehensive user manual. As after sales services to our customers, we provide ALD consulting and process tool maintenance through our offices and worldwide distributor network.
Q: How are the precursor lines of PICOSUN™ ALD tools designed?
A: In properly designed ALD reactors like PICOSUN™ ALD process tools, the precursor lines are separated all the way from source container to the reaction chamber. This enables precursor pulsing without possible precursor cross-reaction and cross-contamination issues. Also unwanted CVD-type growth could easily happen, if the precursors would share the same line. The precursor lines of PICOSUN™ ALD tools have individual mass flow controllers for accurate and highly repeatable processing. They also have individual pressure gauges for pulse pressure monitoring. The precursor lines are very short to enable quick delivery of precursors to the reaction chamber. Our ALD tools are cleverly designed to avoid precursor condensation without extra line heaters. This unique combination of features ensures that the design of our products is evidently the best on the market.
Q: Why is there a dual chamber structure in PICOSUN™ ALD tools?
A: The dual chamber structure means that the reaction chamber is installed inside a vacuum chamber. This kind of structure is safe for the user and enables highly uniform heat distribution inside the reaction chamber. It also prevents water condensation on reaction chamber walls. Condensed water on reaction chamber walls could degrade film quality.
Q: Can I upgrade my PICOSUN™ R-series ALD process tool later on with a substrate loader?
A: Normally PICOSUN™ R-series ALD process tool is equipped with a pneumatic lift, which opens the reaction chamber to atmosphere for quick wafer loading. We have two optional wafer loader options available for R-series ALD process tools. The options are manual and semi-automatic substrate loader. Both options are equipped with a load lock and a gate valve.
Q: What kind of materials can I process with PICOSUN™ ALD tools?
A: The deposition temperature up to 500°C enable processing of virtually all thermal ALD processes, that have been developed. A list of ALD processes can be found for example from article: R.L. Puurunen, Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process, J. Appl. Phys. 97 (12), 121301 (2005).
Q: Can I process oxides and nitrides in the same ALD process tool?
A: In principle it is possible to process oxides and nitrides in one ALD process tool. However, according to our experience e.g. electrical properties of nitrides can degrade if also oxides are processed in the same tool. This is due to easy incorporation of oxygen in nitride films. Especially in production it is crucial to have optimal nitride quality and therefore use an ALD reactor dedicated to nitride processes.
Q: Can I coat porous samples with PICOSUN™ ALD tools?
A: Yes you can. We have a special reaction chamber available for coating through porous substrates. We also have a reaction chamber option for powder coating. And if the open pores are on top of the substrate, coating can be done in our normal reaction chamber for wafers. ALD is an excellent method of conformal coating of porous materials.